“eNJoy House challenges traditional concepts and techniques for building high-performance, energy-efficient homes.”

Richard Garber


Best Sustainable Design Award

eNJoy House in Washington, D.C.

Content on this page requires a newer version of Adobe Flash Player.

Get Adobe Flash player

Every two years, the U.S. Department of Energy hosts a Solar Decathlon, where collegiate teams design, build, and operate solar-powered houses that are cost-effective, energy-efficient, and attractive. In 2011, a team of architecture and engineering students from the New Jersey Institute of Technology (NJIT) and Rutgers University entered the contest with a radical goal: to build the first precast concrete house in the history of the competition.

The team chose a precast concrete home and partnered with Northeast Precast for many reasons, says NJIT associate professor Richard Garber, AIA, who led the team. Precast concrete is low maintenance and durable; it can resist weather, chemicals, and moisture; it can contain natural materials and recycled byproducts to reduce its carbon footprint; and it has low to negligible levels of volatile organic compounds, making it a healthier alternative to standard construction.

However the use of precast concrete also presented several challenges, which is why we turned to Northeast Precast, Garber says. “We enjoyed many unique firsts on this project that had to do with the use of precast in a high-performance and sustainable housing solution.”

To meet the criteria of the decathlon, the house had to be solar powered and no more than 1000 ft2 (93 m2). It would also be judged on 10 objective and subjective criteria, including engineering, affordability, comfort, market appeal, and energy balance.

For the roof, wall, and floor assemblies, the team came up with a design using 27 reinforced concrete panels composed of one layer of expanded polystyrene foam sandwiched between two layers of concrete. The house’s concrete panels are all-in-one modular units, which eliminated the need for additional trades on the building site.

“We pushed the flexibility of concrete in this novel formal and performative solution by utilizing the varied casting processes of our industry partner, Northeast Precast and developing each component and connection to deal with unique conditions,” Garber says.

To meet aesthetic and energy goals, the precast concrete roof was designed in a bowl shape and calibrated for optimal sun angle and rain collection while hiding the photovoltaics and solar collectors, which some consider unattractive. The roof cantilevers over the north facade almost 10 ft (3 m), which helps to create an appealing sense that the heavy precast concrete roof is floating above the clerestory windows directly below.

One of the biggest hurdles for the team was the need to build the house first in New Jersey to demonstrate the concept. That process took five days, which included 48 hours for the precast concrete to set. Then they had to disassemble it, ship it to Washington, DC, and reassemble it on the National Mall, which took another 40 hours.

This constraint played a significant role in the development of the structural systems, says John Ruga, president of Northeast Precast in Millville, N.J. The house is divided into three main components that had to be placed and bolted together. “With pieces as heavy as 45,000 lb (20 tonnes) and as wide as 17 ft (5.2 m), it created some very interesting challenges for erecting and shipping. Each location was different and required very precise coordination.”

Although the house didn’t win the decathlon, it delivered valuable lessons to both the students and the architecture community about the many benefits that precast concrete brings to the sustainability conversation. “One of the most unique things about this project is that it showed the flexibility of precast,” Garber says. “It was a great example of what can happen when a very creative design team and producer agree to collaborate to make a project happen with great engineers.”


Solar Team NJ


Owner and Architect: New Jersey Institute of Technology College of Architecture and Design, Newark, N.J.
Precaster: Northeast Precast, Millville, N.J.
Engineer of Record: ARUP, New York, N.Y.
Contractor: Skanska USA Building Inc., Parsipanny, N.J.
Project Cost: $450,000
Project Size: 1000 ft2 (93 m2)